Ecuador, including the Galápagos Islands, is the smallest of the Andean countries. In South America only Uruguay, Surinam, and French Guiana are smaller. With a land area of approximately 283,000 km˛, Ecuador is about the size of the state of Colorado, U.S.A., or somewhat larger than Great Britain.

For more than 160 years since its independence from Spain, Ecuador laid claim to a much larger area of upper Amazonia, including territory extending eastwards to the mouths of the Napo and Marañón Rivers. Peru disputed Ecuador's territorial claims, and these disputes led to armed conflict between the two countries in 1941, 1981, and 1995. Peru and Ecuador signed a territorial accord in 1942, the Protocol of Rio de Janeiro, but the wording of this document contained a geographical error because the size and extent of the Cenepa River watershed, east of the Cordillera del Cóndor, was not known at the time of the signing. After aerial photographs of the region became available in the late 1940s and the geographical error became apparent, Ecuador called a halt to the physical demarcation of the boundary and later declared the Rio de Janeiro Protocol inapplicable. The official maps of Ecuador continued to depict a large area of Amazonia as Ecuadorian territory. The Cordillera del Cóndor region continued to be a source of tension and conflict between Peru and Ecuador, and both countries established military posts along the disputed border. Following the armed conflict in 1995, the two countries began diplomatic negotiations, with mediation carried out by Brazil, Argentina, Chile, and the U.S.A. Ecuador and Peru signed a new treaty in Brasilia in October 1998, establishing the precise location of the international border and allowing Ecuador access to the main Amazon River through Peruvian ports. A new set of official maps for Ecuador, showing the border with Peru established by the 1998 treaty, will be published soon.

The name Ecuador is Spanish for equator, and the country straddles the geographic equator, from about 1°30'N to 5°S latitude; mainland Ecuador extends from about 75°20'W to 81°W longitude. An important event in the history of world geography was the 1736 geodesic expedition led by the French geographer C. M. de La Condamine, when the region was part of the Spanish Empire. La Condamine and his colleagues measured arcs of the Earth's curvature on the equator near Quito and near Pedernales on the Pacific coast; these measurements enabled the first accurate determination of the size of the Earth and led to the establishment of the international metric system of measurement. The fame brought to the region by the French geodesic expedition evidently influenced the adoption of the name, Republic of Ecuador, when the country gained independence in 1830.

The Instituto Geográfico Militar (IGM) publishes the official maps of Ecuador. Topographic maps of the country at 1:1,000,000 and 1:500,000 scales are available, and a series of topographic sheets at 1:50,000 scale, published gradually during the past 20 years, now cover most of the country except remote areas of the Amazon basin and parts of the Andean slopes. The IGM has also published thematic maps at 1:1,000,000 scale, including geologic, soils, bioclimatic, and Holdridge life zone maps. A branch of the IGM, the Centro de Levantamientos Integrados de Recursos Naturales por Sensores Remotos (CLIRSEN), operates a Landsat and SPOT satellite image receiving station near the Cotopaxi volcano, carries out geographic and natural resource studies using remote sensing data, and sells the satellite imagery to other users.

Ecuador is traditionally divided into four natural regions, a scheme that is followed in this Catalogue: 1) the Pacific Coastal region, in Ecuador called the Costa, which includes the lower, western slopes of the Andes below 1,000 m elevation; 2) the Andes Mountains above 1,000 m, which occupy the central portion of the country, known as the Sierra; 3) the Amazon lowlands east of the Andes, referred to as the Oriente, including the lower, eastern slopes of the Andes up to 1,000 m; and 4) the Galápagos Islands, a volcanic archipelago in the Pacific Ocean 1,000 km west of the mainland.

Ecuador is divided into 21 political provinces (see map on left front endpaper). Each province is largely associated with one of the four geographic regions. The Coastal provinces from north to south are Esmeraldas, Manabí, Los Ríos, Guayas, and El Oro. The Andean provinces are Carchi, Imbabura, Pichincha, Cotopaxi, Tungurahua, Chimborazo, Bolívar, Cañar, Azuay, and Loja. The Amazonian provinces are Sucumbíos, Napo, Pastaza, Morona-Santiago, and Zamora-Chinchipe; the Galápagos Islands are also a province. The correspondence of each province within a particular region is not exact; all Amazonian provinces extend upwards to approximately the summit of the Eastern Cordillera, while several Andean provinces contain considerable areas within the Coastal region.

In 1998 the eastern half of Napo province was recognized as the new province of Orellana, but official maps showing the new province have not yet been produced; we therefore use the pre-1998 boundaries of Napo. The new province of Orellana includes Yasuní National Park, an important area for botanical inventories. Similarly, in 1989 the province of Sucumbíos, which includes the botanically important Cuyabeno Wildlife Reserve, was split off from Napo province. This Catalogue includes the province of Sucumbíos, but herbarium specimens collected prior to 1989 reflect the older boundaries of Napo province.

The coastal region of Ecuador is about 150 km wide from the base of the Andes to the Pacific coastline. A relatively low coastal range of mountains extends parallel to and just inland from the coast, from the city of Esmeraldas in the north to Guayaquil in the south, a distance of about 350 km. The summits of the coastal mountains are mostly between 400 and 600 m elevation, but a few isolated peaks are above 800 m. The coastal range is fairly continuous throughout its length, but is known by different local names: from north to south, the cordilleras of Mache, Chindul, Jama, Colonche, and Chongón.

Between the coastal range and the Andes, south of the equator, is the broad, nearly level Guayas River basin; north of the equator is the valley of the Esmeraldas River. At the mouth of the Guayas River lies Guayaquil, Ecuador's largest city and principal port. The estuary of the Guayas River empties into the Gulf of Guayaquil, the largest embayment of the Pacific Ocean on the South American coast. In the estuary and gulf are a number of low-lying islands, the largest of which is Puná Island. The Santa Elena Peninsula extends west and south of Guayaquil. South of Guayaquil to the Peruvian border there is no coastal range of mountains, and there the coastal region is a narrow lowland strip 25 km wide between the Andes and the Gulf of Guayaquil.

The Andes Mountains are the dominant topographic feature of Ecuador and occupy the central third of the country from the northern to southern borders. In northern and central Ecuador, the Andes form two distinct parallel chains: the Western Cordillera and the Eastern Cordillera; the latter is also known as the Cordillera Real. Between the Western and Eastern cordilleras are a series of intermontane valleys, which are separated from one another by a series of high, transverse east-west-trending ridges referred to locally as nudos (knots). Most of Ecuador's highland cities, including the capital city of Quito, are located in the intermontane valleys. Both the cordilleras are topped by a series of high Quaternary volcanoes; those volcanic peaks that exceed 5,000 m elevation are capped by glaciers. The highest volcano is Chimborazo, at 6,310 m. The major volcanic peaks of the Western Cordillera, from north to south, are: Chiles (along the northern border with Colombia), Cotacachi, Pichincha, Illinizas, and Chimborazo. The major volcanoes of the Eastern Cordillera are Cayambe, Antisana, Cotopaxi, Tungurahua, El Altar, and Sangay.

The Andes of southern Ecuador (Cañar, Azuay, and Loja provinces) are not so clearly differentiated into western and eastern cordilleras, but form a more complex pattern of ridges, some of which trend north-south and some east-west. There are no high, Quaternary volcanoes in southern Ecuador; the highest ridges and peaks are barely above 4,000 m.

Some geographers (e.g., Sauer, 1965) recognize a third cordillera east of the two main chains of the Andes, which is tectonically related to the Cordillera Oriental of Colombia. The third cordillera is not a continuous chain; it forms a series of short ranges, mostly of Cretaceous and Tertiary sediments, including the Cordilleras of Galeras, Cutucú, and Cóndor. The Reventador and Sumaco Volcanoes, in Sucumbíos and Napo provinces, respectively, are part of the third cordillera.

The eastern third of continental Ecuador is part of the upper, westernmost portion of the Amazon River basin. Ecuador occupies only about 2% of the entire Amazon drainage. In Amazonian Ecuador, most of the area of terra firme between the major river valleys is not a flat, featureless plain, but rather a peneplain with a complex micro-topography of low, but often steep-sided hills. Mostly north of the Napo River, Amazonian Ecuador is a truly flat plain. Areas with poor drainage are occupied by swamps and oligotrophic black-water lakes.

Most of the rivers in Ecuador originate in the Andes and flow either west to the Pacific Ocean or east to the Amazon basin. The intermontane valleys between the Eastern and Western Cordilleras drain either west or east so the continental divide is along the Eastern Cordillera in some parts of the Ecuadorian Andes and along the Western Cordillera in other sections. The major river systems flowing to the Pacific, from north to south, are the Chota/Mira, Santiago/Cayapas, Guayllabamba/Esmeraldas, Daule/Babahoyo/Guayas, Chimbo/Chanchán, Jubones, Puyango, and Catamayo/Calvas river basins. The major river systems flowing to the Amazon basin, from north to south, are the San Miguel/Putumayo, Aguarico, Napo, Curaray, Pastaza, Morona, Upano/Paute/Zamora/Santiago, and Chinchipe river systems. The rivers of northern Amazonian Ecuador (except the Putumayo) flow into the Napo and thence into the main Amazon, just downstream from Iquitos, Peru. The southern rivers flow into the Marañón, a major tributary of the Amazon, within Peruvian territory.

The Galápagos Islands, also known as the Archipiélago de Colón, comprise 12 large islands and numerous smaller islands and exposed rocks; the total land area of the Galápagos is about 8,000 km2.